<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .column{
    display:flex;
    flex-direction: column;
    justify-content: center;
  }
  .row{
    display:flex;
    flex-direction: row;
    justify-content: center;
  }
  .box{
    background-color: pink;
    margin: 10px;
  }
  .father{
    width: 500px;
    height: 500px;
    border: 1px solid red;
    align-items: center;
    flex-wrap: wrap;
  }
  .box2{
    align-self: stretch;
  }
  .box3{
    flex: 1;
  }
  </style>
  
</head>
<body>
  <div class="row father">
    <p class="box">段落1</p>
    <p class="box">段落1</p>
    <p class="box">段落1</p>
    <p class="box">段落1</p>
    <p class="box">段落1</p>
    <p class="box">段落1</p>
    <p class="box box2">段落2</p>
    <p class="box box2">段落2</p>
    <p class="box box2">段落2</p>
    <p class="box box2">段落2</p>
    <p class="box box2">段落2</p>
    <p class="box box3">段落3</p>
    <p class="box box3">段落3</p>
    <p class="box box3">段落3</p>
    <p class="box box3">段落3</p>
    <p class="box box3">段落3</p>
    <p class="box box3">段落3</p>
  </div>
</body>
</html>